The effect of the trp repressor from Escherichia coli on the structure and dynamics of dA20dT20

Andrew N. Lane, Jean Francois Lefévre, Oleg Jardetzky

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

We have determined the effect of the tryptophan (trp) repressor from Escherichia coli on the structure and dynamics of dA20dT20. The structure was determined using time-dependent nuclear Overhauser effects and spin-lattice relaxation times. The deoxyribose conformation is near C3′ endo for the thymine residues, and a mixture of about 30% C3′ endo and 70% C2′ endo for the adenine residues. The glycosidic torsion angles are -50° for T and -60° for A. The roll is 20° and the propellor twist is about 29°. The conformation is consistent with recent calculations (Rao, K. and Kollman, P.A. (1985) J. Am. Chem. Soc. 107, 1507-1511). The rate constant for exchange of the imino protons is similar to that usually found for AT base-pairs, with an activation energy of 20 ± 2 kcal/mol, and an activation entropy of 17 ± 7 cal/mol per K. The repressor greatly retards the exchange of imino protons, and the activation energy increases to 38 kcal/mol. There are small changes in the structure of the DNA on forming the complex, with the adenine and thymidine residues becoming more similar in conformation.

Original languageEnglish
Pages (from-to)45-56
Number of pages12
JournalBiochimica et Biophysica Acta - Gene Structure and Expression
Volume867
Issue number1-2
DOIs
StatePublished - May 27 1986

Bibliographical note

Funding Information:
This work was supported by NIH Grant No. RR00711 and NIGMS Grant No. GM33385. A.N.L. is grateful to EMBO for a Long Term Fellowship, and J.F.L. to La Fondation pour la Recherche Medicale for similar support. We thank, too, Drs. R.W. Behling and D.R. Kearns for sending us a preprint of their article on the structure of poly(dA) • poly(dT).

Keywords

  • Imino proton exchange
  • NMR
  • Nucleic acid structure
  • trp repressor

ASJC Scopus subject areas

  • Structural Biology
  • Biophysics
  • Biochemistry
  • Genetics

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